Currently, the most powerful therapy for obesity is bariatric surgery both in terms of
significant weight loss and long-term efficacy. Most surgeons regard the Roux-en-Y
gastric bypass (gastric bypass) operation as “gold standard” for obesity treatment.
However, underlying mechanisms by which gastric bypass induces and sustains
weight loss are not fully understood, but include reduced hunger, increased satiety,
increased energy expenditure, altered taste, as well as reduced preference for foods
with a high fat and sugar content. In fact, gastric patients often report idiosyncratic
changes in taste perception that involves “sweet” taste and a calorie-dense food.
I herein aimed to investigate how gastric bypass reduces intake of and preference
for food high in fat and sugar in rats and humans. I found that the proportion of
dietary fat in gastric bypass patients was significantly reduced six years after surgery
compared with patients after vertical-banded gastroplasty. In addition, gastric bypass
patients had an increased sucrose detection sensitivity compared with before
surgery and controls, but hedonic taste ratings of sucrose in bypass patients
remained unchanged. Rats after gastric bypass exhibit a shift away from high to low
fat food. When compared to sham-operated rats, gastric bypass rats did not prefer
high sucrose and fat concentrations in a two bottle preference test, but preoperative
sucrose exposure reduced this effect. There was no difference in appetitive or
consumatory behaviour in the brief access test between the sham-operated and
gastric bypass rats. An oral gavage of 1 ml corn oil in gastric bypass rats induced
conditioned taste aversion which was also demonstrated after exogenous
administration of the GLP-1 receptor agonist exendin-4 (2 μg/kg intraperitoneal) in
unoperated rats.
These findings suggest that an altered food preference may contribute to long-term
maintained weight loss after gastric bypass. Postingestive effects resulting in
conditioned taste aversion may partially explain this observation
